1. Field of the Invention
The invention relates to blind rivet setting tools which have a mandrel collection system for collecting the pulled (spent) mandrel of the rivets set by the tools. More specifically, the invention relates to a control valve for such a mandrel collection system.
2. Summary of the Prior Art
Power operated blind rivet setting tools are typically utilized for heavy duty continuous assembly line operation, and examples of such tools are illustrated in U.S. patent application Nos. 3,088,618 and 3,254,522. In the use of such tools, it is desirable to provide a means to quickly and efficiently remove the spent mandrel from the rear of the jaw area of the tool. Otherwise, the spent mandrel would have to be removed through the nose of the tool which would prevent quickly inserting another rivet-mandrel assembly into the tool nose for application of the rivet to the workpiece.
Therefore, provision has been made for providing a canister on the rear of the tool and by placing a vacuum in the canister, the spent mandrel is drawn through the tool into the canister. Examples of tools with mandrel collection systems of this type are illustrated in U.S. Pat. Nos. 3,415,102 and 4,281,531.
One manner of providing a vacuum in the canister is by supplying air pressure to a transducer co-acting with the canister which creates a vacuum in the canister to draw the spent mandrel through the tool. In U.S. Pat. No. 4,517,820 there is illustrated a mandrel collection system of this latter type.
In some tools, it is desirable to eliminate the function of the mandrel collection system when removing the canister and thus it becomes necessary to render the air line to the collection system inoperative. Further, air can be conserved by shutting off the mandrel collection system during break periods. In U.S. Pat. No. 4,598,571, a control valve to accomplish these functions is illustrated. In practice, however, it has been found that in order to function properly such valve requires extremely close tolerances and surface finishes. Achieving such tolerances and finishes has proved to be difficult.
The shortcoming of the U.S. Pat. No. 4,598,571 valve were addressed by utilizing a ball-type valve. This valve included a housing with inlet and outlet ports and a spindle located within the housing. The spindle had an aperture adapted to contain a rubber ball and located such that the ball cooperated with the exit port. This valve features one shut-off mode utilizing a manual quarter turn operation. In the "ON" position, the ball is not in contact with the exit port, and air flows around the spindle. In the "OFF" position, the air pressure forces the ball against the exit port, thereby stopping the flow of air.
European patent application Nos. 0201292 and 2302393 disclose a rivet installation tool having a collection system. A valve is disclosed which has an actuating plunger protruding from the base of the tool. When the tool is placed on its base, the plunger is pushed in and the valve shuts off the air supply. When the tool is picked up again, the valve remains off until the tool actuating trigger is operated again. The valve disclosed therein also requires extremely close tolerances to be effective and does not provide two shut-off modes. In particular, the valve does no provide a manual shut-off mode. Finally, the valve of the present invention provides an automatic resumption in air flow when the tool is lifted from the support surface without requiring operation of the trigger .